Liners are sometimes provided for truck beds. The liners can be removable plastic liners, or permanently affixed to the truck bed. The permanently affixed liners are often formed by spraying a material onto the truck bed and allowing the material to harden into a tough, but resilient lining material.
The sprayed material is often a plural component urethane/polyurea material. But typical spraying equipment require a large source of air and high air pressure. Typical applications require minimum of 7 to 11 CFM at 250-3000 psi. This typically requires the use of a very large and heavy 220 volt air compressor usually weighing hundreds of pounds. Further, the performance of the material is very sensitive to temperature, so an 8xe2x80x2xc3x9710xe2x80x2 heating room is typically needed in order to maintain the temperature of the materials at an operating temperature. The spray gun and associated equipment is very complicated and expensive.
There is thus a need for an small, portable and less expensive method and apparatus to spray plural component truck bed liners.
A portable system is provide for spraying viscous materials to form a truck bed liner. Tanks of coating materials that include an activator and resin are contained in a heated, portable cart which also houses a motor driving two pumps to pump the coating materials through air lines to a spray gun at a rate that can be varied by an operator. A high volume, low pressure air compressor is also mounted on the cart and in fluid communication with the air gun. The coating materials are forced through a mixing tube and out of a nozzle tip where it is atomized by the high volume air for spraying to coat the truck bed liner. A pressurized flush tank is activated immediately after spraying in order to clear the coating materials from the spray gun. A modified, dual component caulking gun containing a preselected, second colored resin and activator can be attached to the nozzle tip for decorative coloring or texturing.
The portable system for spraying viscous coating material advantageously comprises a portable cart having an enclosed interior with a heater providing heat to the enclosed interior. A thermostat to regulate the heater and interior temperature in the enclosure can be used to advantage. Plural containers for holding at least two coating materials during use of the system are on the cart, with at least one of the containers having a major portion enclosed within the interior of the cart. At least one high volume, low pressure air compressor is mounted on the cart. A spray gun is placed in fluid communication with the containers and air compressor, the spray gun having a spray nozzle providing mixture of air from the compressor with coating material from the containers, the spray gun further having a static mixing tube within which coating materials are mixed prior to being sprayed by the nozzle. At least one pump is in fluid communication with the containers and static mixing tube to pump coating material from at least two of the containers to the spray gun during use of the system. The coating materials, a resin and an activator, have viscosities of between about 700-2000 centipoise so a suitable pump is needed. Preferably the nozzle mixes the air and coating material external to the nozzle to avoid clogging after spraying is completed.
Advantageously, sufficient compressors are provided to supply the spray nozzle with between 50-100 cfm of air at below about 25 psi. Preferably, sufficient compressors are provided to supply the spray nozzle with air between about 5-10 psi. As needed, two or more air compressors having outlets in fluid communication with a common air line that is connected to the spray gun can be used in order to achieve the needed volume and pressure.
Advantageously, the static mixing tube has static mixing elements extending about xc2xd or less of the length of the static mixing tube in order to only partially mix the coating materials. The tube diameter or length could also be varied to achieve this partial mixing. Preferably, though, the static mixing tube has the number of static mixing elements selected to cause partial mixing of the coating materials to delay curing of the partially mixed coating materials.
After spraying is completed, a pressurized solvent flush tank in fluid communication with the static mixing tube is used to flush the components before the coating materials set. Preferably, the solvent tank is mounted to the spray gun, with an actuating valve interposed between the tank and the spray gun to allow pressurized fluid from the tank to enter the mixing tube. The pressure is preferably sufficient to clear any partially set coating materials.
To ensure uniform spraying, it is desirable to have high pressure lines place the material pump in fluid communication with the spray gun. Teflon lined lines, with high strength, but flexible steel braiding are desirable.
In a further embodiment a modified dual element caulking gun containing a tube of a second resin and a tube of activator can be placed in fluid communication with the mixing tube. This allows additional colors to be added to the coating.
There is thus provided a portable system for spraying viscous coating material onto a surface, including a portable cart having an enclosed interior and an electrically powered heater in communication with a temperature sensor to regulate the temperature of the enclosed interior. The system includes temperature controlled containers for coating materials including at least one container for an activator and one container for a resin each of which are enclosed sufficiently in the interior of the cart so the heater can maintain the temperature of the coating materials in the containers at a predetermined minimum temperature during use of the system. The system further includes a high volume, low pressure air compressor mounted on the cart for providing compressed air to the spray through air lines placed in fluid communication with means for spraying mixed coating materials. The means comprises an external mixture of air from the compressor with coating material from the containers. The system further comprises a source of pressurized solvent in fluid communication with the spray means for spraying, and a valve interposed between the source of solvent and the spray means to allow solvent to pass from the source to the spray means when the valve is actuated.
There is also advantageously provided a method for spraying coating materials onto a surface. The method provides plural coating components to a static mixing tube without mixing at least two of the components which include a resin and an activator, by pumping the components from temperature controlled tanks through separate material lines to the mixing tube. The method further includes partially mixing the activator and resin in the mixing tube by using one of a tube length, tube diameter, or fewer than the number of static mixing elements needed to thoroughly mix the activator and resin within the tube in order to delay curing of the partially mixed materials. The method also provides the partially mixed materials to an external air-mixture spray nozzle at a predetermined rate by using pumps. High volume, low pressure air is provided at below about 10 psi to the external air-mixture spray nozzle to spray the material onto the surface to be coated.
The method further, but optionally, comprises flushing the mixing tube and nozzle with pressurized solvent by opening a valve that controls the flow of solvent to the tube. Moreover, the method can comprise placing a tube of a second resin and a tube of activator in fluid communication with a mixing tube that is in fluid communication with the nozzle and forcing the second resin and activator from their tubes and through the mixing tube and nozzle in order to spray the second resin onto the coated surface. For storage, the method includes disconnecting the spray gun and connecting the lines transporting the coating materials to the tanks for the respective materials, and periodically pumping the material through the lines. Advantageously, the material lines are placed inside the heated interior of the cart in order to avoid hardening or setting of the materials.